Helmet mounted displays allow for the simultaneous viewing of visual information and/or images generated by a computer or other source, together with and/or superimposed on a direct viewing of an external scene. Such helmet mounted displays are used in many areas including training, entertainment and military applications such as aircraft pilots. Aircraft pilots find such displays useful in furnishing information relating to aircraft operation, weather radar presentations, maps, weapons aiming, and other such information as would be useful or desirable while flying.
In some displays, the visual information or visual images are superimposed on an optical combiner mounted on the head gear, a helmet visor for example, in view of the eye of the wearer such as the observer""s line of sight. In helmet mounted displays, in order for a display image to be viewed by the user""s eye, sufficient contrast against the background scene must exist to allow the image to be clearly viewed. For example, during the daytime, it would be difficult for an observer to view a display image as well as the external scene due to the brightness of daytime.
To assure that the contrast is provided in high ambient conditions, the display image must either be of high luminance or the background luminance must be attenuated. However, capabilities to provide a good contrast have resulted in high cost, high energy use or complex configurations. It would be desirable to have a simple, low cost implementation to provide a great contrast in helmet displays that requires little energy. Further, it would be desirable to have an implementation in which the helmet user could control the contrast.
A helmet apparatus to improve viewing of a display image as well as an external scene includes a combiner placed over one eye of the user. The combiner is coated with a material which attenuates light to provide a contrast between the combiner and ambient light conditions. The apparatus automatically attenuates the combiner when ambient light is sensed by a light sensor. The combiner will attenuate more if the ambient light is greater. The combiner attenuation may also be controlled manually based on the user""s desire.